Laboratory Assessment of NETs

Abstract

The diagnosis of pancreatic neuroendocrine tumors (pNETs) is based upon: (a) the clinical features, especially in functioning tumors, (b) the levels of several peptides and amines, that represent tumor products, in blood and urine (biomarkers), (3) the localization of primary and/or metastatic lesions by imaging studies, and (4) the histopathological confirmation (through a biopsy or a surgical specimen) which represents the “gold standard” and should be obtained whenever possible. The laboratory assessment of pNETs is based on biomarkers that are used for confirmation the diagnosis, follow-up assessments, as well as prediction and monitoring of treatment response. Biomarkers may be specific for a clinical syndrome associated with these tumors, whereas others are thought to be non-specific (general), as they are secreted by a variety of neuroendocrine cells. Fasting gut hormones represent the most commonly used specific biomarkers in functioning pNETs, whereas Chromogranin-A (CgA) is the only established non-specific (general) biomarker for all NETs. Several factors need to be taken into account when interpreting CgA levels, as certain drugs or clinical entities may be associated with its increased levels. The role of currently used biomarkers for prognosis has not been established in pNETs. Novel biomarkers such as circulating tumor cells seem promising.